This work describes the identification and characterization of SurR, Pyrococcus furiosus sulphur (S(0)) response regulator. SurR was captured from cell extract using promoter DNA of a hydrogenase operon that is downregulated in the primary response of P. furiosus to S(0), as revealed by DNA microarray experiments. SurR was validated as a sequence-specific DNA binding protein, and characterization of the SurR DNA binding motif GTTn(3)AAC led to the identification of several target genes that contain an extended motif in their promoters. A number of these were validated to contain upstream SurR binding sites. These SurR targets strongly correspond with open reading frames and operons both up- and downregulated in the primary response to S(0). In vitro transcription revealed that SurR is an activator for its own gene as well as for two hydrogenase operons whose expression is downregulated during the primary S(0) response; it is also a repressor for two genes upregulated during the primary S(0) response, one of which encodes the primary S(0)-reducing enzyme NAD(P)H sulphur reductase. Herein we give evidence for the role of SurR in both mediating the primary response to S(0) and controlling hydrogen production in P. furiosus.